Mobile energy carrier and energy store

ABSTRACT

A mobile energy carrier with which energy in the form of materials from zones distributed widely throughout the world, for example with a large amount of solar energy, wind energy or other CO 2 -neutral energy, for example the equator, can be transported to zones where there is a high energy requirement, for example Europe.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the U.S. national stage of International Application No. PCT/EP2009/058081, filed Jun. 29, 2009 and claims the benefit thereof. The International Application claims the benefits of German Application No. 102008031437.4 filed on Jul. 4, 2008, both applications are incorporated by reference herein in their entirety.

BACKGROUND

Described below is a mobile energy carrier and energy store, by which energy can be transported in the form of material from zones distributed widely throughout the world, for example with a large amount of solar energy, wind energy or other CO₂ neutral energy, such as the equator, to zones with a high energy demand, for example Europe.

It is a general problem that energy is scarce and expensive, the worldwide oil reserves are limited, and the CO₂ emission from energy use must be controlled.

There is therefore always a requirement to create energy carriers which provide useable energy carriers, which are as CO₂ neutral as possible, in the industrial zones.

Some efforts have already been made to make the energy stored in naturally occurring rocks or sand usable beyond national boundaries. Particularly in conjunction with silicon extraction, trials have already been carried out to obtain energy from quartz or sand. This is done using compounds which are analogous to hydrocarbons and which have to be obtained chemically via a number of energy-intensive intermediate steps.

However, until now, this has always failed because of the negative energy balance which results when all the factors are considered, such as release of the energy contained therein, transport, etc.

SUMMARY

An aspect is therefore to provide a mobile energy carrier by which energy, for example in the form of solar energy, can be absorbed at the equator and can be released again in central Europe with a positive energy balance. However, the energy carrier can also be used to store excess energy in industrial countries.

An energy carrier may be in the form of elementary metal, wherein the metal is an electropositive metal. The use of an electropositive metal as an energy carrier and energy store is also described.

The expression energy carrier in the present case means a material which solves the stated problem, that is to say absorbs the CO₂ neutral and renewable energy all around the globe, can then transport it as cost-effectively as possible, and can release the stored energy again, at any time.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The energy carrier is suitable for being used directly in the form of primary electrochemical cells for electricity generation, by reaction with nitrogen in the air to produce fertilizers, and at the same time to produce thermal energy, and solely by combustion for energy production. The energy carrier resides well at the start of a possible energy chain.

The production of solar cells allows the direct conversion of sunlight to electrical energy. The energy carrier and energy store proposed for the first time here can be used to store photovoltaicly produced energy.

A metal is preferably used, which is available in adequate quantities. With a proportion of 0.006% of the earth's surface, the natural availability of lithium is comparable to that of copper and tungsten. In comparison to the other alkali metals and alkaline earth metals, lithium has advantages in terms of transport characteristics and the release of the energy. Further electropositive elements should also be mentioned, which can be considered as energy stores and energy carriers, such as zinc, magnesium, aluminum and/or the lanthanides, which likewise occur in a sufficient quantities and can be used as energy carrier here.

The metal is preferably a highly electropositive metal, which is also light in weight. Metals such as lithium are particularly suitable. With a density of 0.534 g/cm³, lithium is the lightest of all the solid elements, after solid hydrogen.

Because of the special electron configuration of lithium in elementary form, this metal is the most electropositive of all, since the readiness to emit the single electron to the 2 s shell is very high. Lithium thus has the most negative potential of all of −3.045 volts.

Therefore, the energy storage cycle takes place as follows: first of all, the energy carrier lithium is produced from the naturally occurring lithium carbonate, and salts derived therefrom are produced by molten mass electrolysis.

It reacts strongly with water and air, but less strongly than the other alkali metals such as sodium and potassium.

It can accordingly preferably be transported in the form of solid bulk units such that there is as little surface area as possible for air and water to act on. Lithium can, for example, be melted by solar-thermal action, and can be pumped in liquid form. The energy carrier can be solidified for storage. This likewise applies to other alkali metals and, to a lesser extent, also to zinc.

An alternative transport form is also lithium hydride which is transported in solid form. It is also feasible to use other lithium derivatives, such as complex lithium compounds.

The reaction with water or oxygen in the air is primarily used to release the energy. The resultant hydroxides or oxides are once again fed back into the cycle.

The products which are created during the reaction with oxygen or water in the event of an accident are all water-soluble and neutralized by CO₂. In contrast to nuclear energy, there is therefore no need to expect any long-term damage to the environment.

Lithium is already used as an active material in negative electrodes. Because of the standard potential of approximately −3.5 volts for electrochemical cells (the most negative of all chemical elements, the high cell voltage which can be produced by, and the high theoretical capacity of 3.86 Ah/g make lithium an “ideal” negative electrode material (cathode material) for electrochemical cells. Electrical energy can thus be obtained in primary electrochemical cells, for example in conjunction with an air anode.

The use of lithium is described by way of example, which has advantages in use of the proposed mobile energy carrier in comparison to the prior art, for example energy obtained from oil.

Lithium can be produced electrochemically from naturally occurring rocks or waste products from sodium-potassium salt processing (in the form of the carbonate) by electrolysis, in particular by melt electrolysis. Lithium hydride can be produced directly from the elements by a solar-thermal reaction at an increased temperature.

All types of renewable energies can be used for electrolysis. In particular, wind energy, solar energy, biogas energy or overproduction from nuclear power stations can be used to obtain the pure lithium in elementary form.

The lithium is transported in the form of the pure metal or in the form of the hydride. In this case, precautionary measures are required, although, for example, the metal can be carried in double-hulled ships for sea transportation, in which the environmental risks of transport are less than those in the case of oil transportation, because all the reaction products with water or oxygen in the air with lithium are water-soluble.

Lithium (0.54 g/cm³) or lithium hydride (0.76 g/cm³) have a considerably lower density than water. Ships or containers which are loaded with the energy store are therefore unsinkable. This also applies to a restricted extent to the other alkali metals.

By way of example, for loading and unloading, the lithium metal, which has a comparatively low melting point of about 180° C. can be pumped. Lithium has the widest liquid range of all alkali metals.

In the form of the pure metal or of the metal hydride, the electropositive metals such as lithium and their homologous metals sodium, potassium as well as zinc, aluminum, magnesium and the lanthanides, can accordingly be used as energy carriers.

It is therefore proposed that elementary metal such as lithium or lithium hydride be produced using renewable energy at suitable points throughout the world, and that the metal then be transported in suitable containers, which, for example, are hermetically sealed against air and oxygen, to Europe or to other energy-consuming zones, where the potential energy stored in the metal or metal hydride can be released in an environmentally neutral manner by reaction with oxygen (“combustion”) or with water.

The thermal energy which is released during combustion of lithium is −599.1 kJ/mol or −143.1 kcal/mol or −20.4 kcal/g and is approximately three times as great as that of coal.

However, in contrast to coal, no off-gas problem will occur from lithium combustion, since lithium quantitatively burns to form the oxide, which need not be stored but from which the metal is obtained in pure form after again being suitably transported to a suitable point in the world.

Even more energy is released when the metal reacts with water. The resultant waste product is lithium hydroxide, which can likewise be used as a raw material for obtaining lithium, in the same way as the oxide which is obtained from burning.

A further important advantage of lithium as an energy store is direct access to the production of fertilizers, which are essential for supplying the population of the world with food. It could likewise be used, although with low efficiency, for obtaining bio gas.

In this case, lithium reacts directly with oxygen in the air to form lithium nitride. The reaction takes place slowly, even at room temperature, but can be controlled by increasing the temperature. Following this, lithium nitride reacts with water to form ammonia and lithium hydroxide. Ammonia represents one of the most important sources of nitrogen for the chemical industry. Large amounts of ammonia are used for the production of fertilizers. In the process, large amounts of thermal energy are released. Ammonia can be burnt using the Ostwald process. The nitric acid which is created in this case is neutralized by ammonia. The resultant ammonium nitrate can be used directly for agriculture.

The use of lithium as an energy carrier and energy store therefore allows fertilizers to be produced without use of fossil fuels. In this case, solar energy is stored in a high-quality fertilizer. Lithium acts as the mediator.

A primary electrochemical cell is an energy store, for example an electrochemical element, in which the stored energy is immediately available and which—in contrast the secondary electrochemical cells—so-called rechargeable batteries, can in principle not be charged again.

Proposed is the use of an electropositive metal, in particular lithium, to solve the general energy problem. In this context, it has surprisingly been found that lithium is actually more suitable for the transport of energy, with considerably reduced risks to the environment than crude oil because of its lightness, its extreme normal potential and its wide liquid range. This is particularly because lithium forms water-soluble products when it reacts with water or oxygen which, once they have reacted, can be neutralized with CO₂ (1 g LiOH reacts with 450 ml of CO₂). In addition, lithium is used to fix nitrogen in the air, in order to make it useable for biological cycles, for example in the fertilizer industry.

A description has been provided with particular reference to preferred embodiments thereof and examples, but it will be understood that variations and modifications can be effected within the spirit and scope of the claims which may include the phrase “at least one of A, B and C” as an alternative expression that means one or more of A, B and C may be used, contrary to the holding in Superguide v. DIRECTV, 358 F3d 870, 69 USPQ2d 1865 (Fed. Cir. 2004). 

1-8. (canceled)
 9. A method for energy transport and/or energy storage, comprising: obtaining electrical energy from at least one of sun, wind, biogas, and excessively produced electrical energy; producing, from the electrical energy, an energy carrier formed as an elementary metal; changing the energy carrier to a transportable or storable species; transporting or storing the energy carrier in the transportable or storable species; and releasing the electrical energy stored in the energy carrier by reaction with at least one of water and oxygen.
 10. A mobile energy carrier and/or energy, comprising: an elemental electropositive metal.
 11. The mobile energy carrier as claimed in claim 10, wherein the elemental electropositive metal is a transportable and/or storable form of at least one among the group of lithium alloy, lithium hydride and a lithium derivative.
 12. The mobile energy carrier as claimed in claim 10, wherein the elemental electropositive metal comprises an alkali and/or alkaline earth metal.
 13. The mobile energy carrier as claimed in claim 10, wherein the elemental electropositive metal comprises at least one of the group of zinc, magnesium, aluminum, and a lanthanide group metal.
 14. The mobile energy carrier as claimed in claim 10, wherein the elemental electropositive metal is produced from an oxygen compound as a raw material.
 15. A method of producing fertilizers containing nitrogen, comprising: forming lithium nitride from lithium; and forming fertilizer from the lithium nitride.
 16. Primary electrochemical cells, comprising: lithium. 